《光通信技术》课件：Lecture8

DepartmentofOpticalEngineeringAReviewchecklistReceiverPartsofReceivermodulePhotodiodeCouplingopticsPreampQuantizerFilterAmp/limiterDecisioncircuitClockrecoveryPhotodiodePINSiliconandInGaAsWideBWHighQEAPDHighsensitivityM~20Highreversebias20VCommoncharacteristicsResponsivityInputpowerv.s.outputIRv.s.wavelengthBandwidthTransittime(driftanddiffusionvelocity)Timeconstant(capacitance)QuantumefficiencyNoiseAnalysis-NoisesourcesShotnoiseThermalnoiseDarknoise1/fnoiseSNRBERQuantumlimit->absoluteminimumP(n)=exp(-Np)(Np)n/n!BER=0.5(P(1/0)+P(0/1))=0.5exp(-Np)LiteratureReadingReportChooseyourreadingtopic:fromreferencelist(downloadfromfiber2013@163.com)Nolongerthan3pagesReportmustbewritteninyourownwordsYourunderstandingonExistingproblemsSolutionsproposedYourevaluationofresultsHandin(tomeortoRoom411)beforefinalexam(June29th)DepartmentofOpticalEngineeringDepartmentofOpticalEngineeringComponentsofFiber-opticNetworksAnoverviewoffiber-opticnetworksPoint-to-pointlinksNetworksANetworkisasetofnodesconnectedbyalinkRedirectingamessage-mostdistinguishingfeatureofanetwork

DepartmentofOpticalEngineeringComponentsofFiber-opticNetworksAnoverviewoffiber-opticnetworksPoint-to-pointlinksNetworksANetworkisasetofnodesconnectedbyalinkRedirectingamessage-mostdistinguishingfeatureofanetworkswitching,routingCircuitswitchingPacketswitchingMultiplexingTime-divisionmultiplexingWavelength-divisionmultiplexingDepartmentofOpticalEngineeringComponentsofFiber-opticNetworksAnoverviewoffiber-opticnetworksMultiplexingTime-divisionmultiplexingWavelength-divisionmultiplexingTDM+WDMDepartmentofOpticalEngineeringAnoverviewoffiber-opticnetworksAdd/DropTDMWavelength-selectiveAdd/DropmultiplexerRe-configurableAdd/DropmultiplexerWDMBroadcast-select->filtersWavelengthrouting->wavelengthrouterDepartmentofOpticalEngineeringAnoverviewoffiber-opticnetworksRepeatersandamplifiersRegenerateasignal->3RRegenerationwithretimingandreshaping3RrepeaterproducesafreshcopyofreceivedsignalRepeatersdonotworkforfiber-opticnetworks,wheremanytransmitterssendsignalstomanyreceiversatdifferentbitratesandindifferentformats->needforanopticalamplifierOpticalamplifierIncreasethecapacityoffiber-opticlinksbyusingWDMProvidethecapabilityofall-opticalnetworks,notjustpoint-to-pointlinksDepartmentofOpticalEngineeringAlistofcomponentsTransmittersandreceiversOpticalamplifiersPassivecomponentsCouplers/splittersWDMmultiplexersanddemultiplexersFiltersIsolatorsCirculatorsAttenuatorsSwitchesWavelengthconvertersOpticaladd/dropmodulesOpticalcross-connectsAplethoraofdifferentdesignsforthesecomponents!DepartmentofOpticalEngineeringTransmitterrequirementsChannelspacing->ITUgridf=(c)/2@1550nm0.8nm->100GhzQualityofgeneratedlightLinewidth<1GHz,DFB10-40MHztoavoidchannelcrosstalkSidemodesuppressionratio35-40dBSinglelongitudinalmodeChirphastobeeliminated->externalmodulationStabilityOutputpowerPeakwavelengthandlinewidthRelativeintensitynoiseDepartmentofOpticalEngineeringTransmitterrequirementsWavelengthrequirement:C-BandorL-BandConventional1520–1560nm40nm->40channelsLong-wavelength1560–1620nm80nm->80channelsupDepartmentofOpticalEngineeringTunablelaserTemperaturetuning0.3nm/CTemperaturedependenceofrefractiveindexExternal-cavitytunablelaser(mstuningtime)Turning/MovinggratingTurning/MovingmirrorDepartmentofOpticalEngineeringTunablelaserExternal-cavitytunablelaser(mstuningtime)MovingfilterArrayofactiveelementsDepartmentofOpticalEngineeringTunablelaserSectionaldistributedBraggreflectionI1forlasergainI2forphaseshiftofreflectedbeam->finetuningI3forBragggrating->changerefractiveindex->coarsetuningNanosecondtuningtimeTuningrange10(3-section)-100nm(4-section)Integrated-cavitylaser3nstuning(selecting)timeActivateindividualgainmedium75GHzchannelspacingDepartmentofOpticalEngineeringRequirementsforreceiversGeneralconsiderationsWavelengthrange1520-1560nm->1620nmSelectingadesiredchannelTunabletransmitterandfixedreceiver(TTFR)Fixedtransmitterandtunablereceiver(FTTR)Activeapproach:onereceiverplusatunablefilterPassiveapproach:anarrayofreceiversRequirementsinWDMSpectralwidth1520-1560nmandresponseflatteningSensitivityforBER,especiallyfornarrowchannelspacingTuningtime:msforconnection-orientednetworks,nsforpacket-switchingTemperaturesensitivity-40->85CPolarizationindependenceDepartmentofOpticalEngineeringOpticalamplifierGeneralconsiderationsTypesSemiconductorFiberFunctionaltypesBooster,post-amplifiermagnifiesatransmittersignalformorepowerIn-lineamp.LownoiseFlatgainPre-ampHighgainLownoiseDepartmentofOpticalEngineeringErbium-dopedfiberamplifier(EDFAs)Three-levelsystem1480nmor980nmpumping1500-1600nmfluorescenceASE:amplifiedspontaneousemissionVastmajorityofions/carriesinSOAareforcedbystimulatedemissiontofalltoalowerlevelSomeofthemdosospontaneouslyThesespontaneouslyemittedandamplifiedphotons->ASERandominphaseGeneratenoiseDepartmentofOpticalEngineeringErbium-dopedfiberamplifier(EDFAs)Gain(dB)=10log(Pout/Pin)TakeoffASEnoise:Gain(dB)=10log[(Pout-PASE)/Pin]GainsaturationGaingoesdownwithinputNoisefigure:

Fn=(SNR)in/(SNR)outexamplesDepartmentofOpticalEngineeringErbium-dopedfiberamplifier(EDFAs)GainandnoiseasafunctionofEDFAparametersLengthofactivefiberInputpowerSignalwavelengthDepartmentofOpticalEngineeringErbium-dopedfiberamplifier(EDFAs)EDFAfiberSmallcore(3-6m)forhighefficiencyCouplingproblemDown-taperingUp-taperingInterimDepartmentofOpticalEngineeringErbium-dopedfiberamplifier(EDFAs)EDFAmoduleGainflatteningfilter(GFF)DepartmentofOpticalEngineeringErbium-dopedfiberamplifier(EDFAs)EDFAmoduleTwopumpingschemesDepartmentofOpticalEngineeringDepartmentofOpticalEngineeringHomeworkProblemsforchapter12Reviewthesummaryofthechapter12.12,12.29,12.58,12.70,12.77,12.85In-ClassQ1DepartmentofOpticalEngineeringNoiseinanopticalamplifierismainlycausedbyA:shortnoiseofphotonspropagatinginfiberB:amplifiedspontaneousemissionC:powerfluctuationofpumpinglaserD:longErlifetimeinitsexcitedstateIn-ClassQ2DepartmentofOpticalEngineeringWhichofthefollowingisnotatypicalopticalamplifierintelcom?A:in-lineopticalamplifierB:powerboosterfor20mWC:poweramplifierfor20WD:pre-amplifierDepartmentofOpticalEngineeringA:Gainofco-propagatingpumpingincreaseswithErdopedfiberlength.B:Noiseinthecaseofcounter-propagatingpumpingishighwhenfiberistoolong.C:temperaturetuningofanlaserdiodecanmeettheneedofC-band.In-ClassQ3true(A)orfalse(B)DepartmentofOpticalEngineeringCouplers–fusedbiconicaltaper(FBT)DepartmentofOpticalEngineeringPowerpropagationofa1x2couplerPowerdistributionZ=couplingregionCouplinglengthLc=/[2k()]DepartmentofOpticalEngineeringCharacteristicsofaWDMcouplerExcessLoss(energyconservation)InsertionlossDirectivityReturnlossIsolationDepartmentofOpticalEngineeringMuxandDemuxCharacteristicsNumberofchannelsCenterwavelengthChannelspacingBandwidthMaximuminsertionlossUniformityIsolationDepartmentofOpticalEngineeringAll-fiberWDMsDepartmentofOpticalEngineeringDemux:ArrayedwaveguidegratingAWGDepartmentofOpticalEngineeringDemux–grating+mirror/GRINlensDepartmentofOpticalEngineeringDWDMfiltersDielectricnarrowbandthin-filmfilterDepartmentofOpticalEngineeringWDMDemux–3portarrayDWDMfilters+collimator=3portsThermalstabilityconsiderationDepartmentofOpticalEngineeringAdd/Dropmultiplexer–BragggratingBragggratingReflectsonechannelFixedconfigurationTemperaturesensitiveDepartmentofOpticalEngineeringIsolator–opticaldiodeDepartmentofOpticalEngineeringCirculator–opticaldirectionalcouplerPartsinvolvedPolarizationbeamsplitterFaradayrotatorNon-reciprocalrotationHalf-waveplateDepartmentofOpticalEngineeringDepartmentofOpticalEngineeringAlightbeamlaunchedintoport1issplitintotwobeamsbythepolarizationbeamsplitterthattransmitsthelightwithhorizontalpolarization(alongthey-axis)andreflectsthelightwithverticalpolarization(alongthex-axis).Thetwobeamsarethenpassedthroughahalf-waveplateandaFaradayrotator.Theopticaxisofthehalf-waveplateisarrangedat22.5°tothex-axissothattheverticallypolarizedlightisrotatedby+45°.ThethicknessoftheFaradayrotatorisselectedforproviding45°-polarizationrotationandtherotationdirectionisselectedtobecounter-clockwisewhenlightpropagatesalongthez-axisdirection.Thepolarizationofthetwobeamsisunchangedafterpassingthroughthehalf-waveplateandFaradayrotatorbecausethepolarizationrotationintroducedbythehalf-waveplate(+45°)iscancelledbythatoftheFaradayrotator(-45°).Thetwobeamsarerecombinedbythesecondpolarizationsplitter

andcoupledintoport2.Similarly,whenalightbeamislaunchedintoport2,itissplitintotwobeamswithorthogonalpolarizationbythesecondpolarizationbeamsplitter.Duetothenon-reciprocalr